<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /*三角本质*/
        .test1{
            height:0;
            width: 0;
            border-top: 50px solid pink;
            border-bottom: 50px solid red;
            border-left: 50px solid blue;
            border-right: 50px solid gold;
        }
        /*单三角效果*/
        .test2{
            height:0;
            width: 0;
            border: 50px solid transparent;
            border-top: 50px solid pink;
        }

    </style>
</head>
<body>
    <div class = "test1"></div>
    <div class = "test2"></div>
</body>
</html>